scholarly journals Thermo-Economic Optimization of a Solid Oxide Fuel Cell, Gas Turbine Hybrid System

2006 ◽  
Vol 4 (2) ◽  
pp. 123-129 ◽  
Author(s):  
N. Autissier ◽  
F. Palazzi ◽  
F. Marechal ◽  
J. van Herle ◽  
D. Favrat
Keyword(s):  
Fuel Cells ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
High Efficiency ◽  
Integrated System ◽  
Solid Oxide ◽  
Inlet Temperature ◽  
Optimization Approach ◽  
Oxide Fuel

Large scale power production benefits from the high efficiency of gas-steam combined cycles. In the lower power range, fuel cells are a good candidate to combine with gas turbines. Such systems can achieve efficiencies exceeding 60%. High-temperature solid oxide fuel cells (SOFC) offer good opportunities for this coupling. In this paper, a systematic method to select a design according to user specifications is presented. The most attractive configurations of this technology coupling are identified using a thermo-economic multi-objective optimization approach. The SOFC model includes detailed computation of losses of the electrodes and thermal management. The system is integrated using pinch based methods. A thermo-economic approach is then used to compute the integrated system performances, size, and cost. This allows to perform the optimization of the system with regard to two objectives: minimize the specific cost and maximize the efficiency. Optimization results prove the existence of designs with costs from 2400$∕kW for a 44% efficiency to 6700$∕kW for a 70% efficiency. Several design options are analyzed regarding, among others, fuel processing, pressure ratio, or turbine inlet temperature. The model of a pressurized SOFC–μGT hybrid cycle combines a state-of-the-art planar SOFC with a high-speed micro-gas turbine sustained by air bearings.

The Effect of Size on Optimisation of Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycles

2009 ◽  
Author(s):  
Michael J. Brear ◽  
Michael J. Dunkley
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Total Power ◽  
Oxide Fuel ◽  
Component Size ◽  
System Pressure

The integration of high temperature solid oxide fuel cells with gas turbines to form high efficiency, hybrid generators is receiving significant attention within both the academic and industrial communities. Various systems have been proposed or demonstrated, and which cover a range of sizes from low power generators suitable for domestic power generation through to larger systems in the megawatt size range. The performance of such hybrid systems depends on the matching of the fuel cell and gas turbine through optimisation of the system pressure ratio and reactant flow rates. Losses associated with non-ideal cycle components are significant and vary with component size, and must be taken into account if optimal performance is to be achieved. This paper presents an intentionally very simple numerical model of the hybrid system, so that the effect of key component efficiencies on the overall cycle efficiency can be examined easily. These component efficiencies of course scale with size, and the results presented suggest that hybrid cycles with total power output of order several MW are preferable.

Investigating the Integration of a Solid Oxide Fuel Cell and a Gas Turbine System With Coal Gasification Technologies

2003 ◽  
Author(s):  
Dawson A. Plummer ◽  
Comas Haynes ◽  
William Wepfer
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Coal Gasification ◽  
High Efficiency ◽  
Integrated System ◽  
Solid Oxide ◽  
Operating Voltage ◽  
Oxide Fuel ◽  
Hybrid Power

Solid oxide fuel cell (SOFC) technology incorporates electrochemical reactions that generate electricity and high quality heat. The coupling of this technology with gas turbine bottoming cycles, to form hybrid power systems, leads to high efficiency levels. The purpose of this study is to conceptually integrate the hybrid power system with existing and imminent coal gasification technologies through computer simulation. The gasification technologies considered for integration include the Kellogg Brown Root (KBR) Transport Reactor and Entrained Coal Gasification. Parametric studies were performed to assess the effect of changes in pertinent fuel cell stack process settings such as operating voltage, inverse equivalence ratio and fuel utilization will be varied. Power output, system efficiency and costs are the chosen dependent variables of interest. Coal gasification data and a proven SOFC model program are used to test the theoretical integration. Feasibility and economic comparisons between the new integrated system and existing conventional systems are also made.

scholarly journals Parametric Study of Fuel Cell and Gas Turbine Combined Cycle Performance

1997 ◽  
Author(s):  
Dawn Stephenson ◽  
Ian Ritchey
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Solid Oxide ◽  
Simple Cycle ◽  
Cycle Performance ◽  
Oxide Fuel ◽  
Combined Cycles

A number of cycles have been proposed in which a solid oxide fuel cell is used as the topping cycle to a gas turbine, including those recently described by Beve et al. (1996). Such proposals frequently focus on the combination of particular gas turbines with particular fuel cells. In this paper, the development of more general models for a number of alternative cycles is described. These models incorporate variations of component performance with key cycle parameters such as gas turbine pressure ratio, fuel cell operating temperature and air flow. Parametric studies are conducted using these models to produce performance maps, giving overall cycle performance in terms of both gas turbine and fuel cell design point operating conditions. The location of potential gas turbine and fuel cell combinations on these maps is then used to identify which of these combinations are most likely to be appropriate for optimum efficiency and power output. It is well known, for example, that the design point of a gas turbine optimised for simple cycle performance is not generally optimal for combined cycle gas turbine performance. The same phenomenon may be observed in combined fuel cell and gas turbine cycles, where both the fuel cell and the gas turbine are likely to differ from those which would be selected for peak simple cycle efficiency. The implications of this for practical fuel cell and gas turbine combined cycles and for development targets for solid oxide fuel cells are discussed. Finally, a brief comparison of the economics of simple cycle fuel cells, simple cycle gas turbines and fuel cell and gas turbine combined cycles is presented, illustrating the benefits which could result.

Comparison of Molten Carbonate and Solid Oxide Fuel Cells for Integration in a Hybrid System for Cogeneration or Tri-Generation

2004 ◽  
Author(s):  
Georgia C. Karvountzi ◽  
Clifford M. Price ◽  
Paul F. Duby
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cells ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Molten Carbonate ◽  
Hybrid Cycle

High temperature fuel cells, such as molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC) can be integrated in a hybrid cycle with a gas turbine and a steam turbine and achieve overall lower heating value (LHV) efficiencies of about 70%. A hybrid cycle designed for cogeneration or tri-generation applications could lead to even higher overall LHV efficiencies. Tri-generation is the combined generation of power, heat and cooling from the same fuel source. The purpose of the present paper is to compare the performance of a 20MW MCFC system and a 20MW tubular SOFC system and assess their potential to cogeneration and tri-generation applications. The system includes a fuel cell, a gas turbine, a multiple pressure heat recovery steam generator (HRSG), a steam turbine and an absorption chiller (for cooling). The systems were designed and sized using GatecycleTM heat balance software by GE Enter Software, LLC. In order to optimize each system we developed curves showing LHV “electric” and “cogeneration” efficiency versus power for different ratios of “MCFC and SOFC fuel cell-to-gas turbines size.” At atmospheric pressure and at 675°C (1247°F) the 20MW MCFC system achieves “electric” efficiency of 69.5%. The SOFC at the same pressure and at 980°C achieves 67.3% “electric” efficiency. The MCFC alone is more efficient (58%) than the SOFC alone (56%). However the SOFC produces more heat than the MCFC leading to slightly higher cogeneration and tri-generation efficiencies. Pressurized operation at 9atm boosts the performance of the SOFC system to higher efficiencies (70.5%). Pressurized operation is problematic for the MCFC due to increased cathode corrosion leading to cathode dissolution as well as sealant and interconnection problems. However we can pressurize the MCFC system independently of the fuel cell with the integration of a gas turbine with a compressor pressure ratio of 10 to 16. Thus we achieve efficiencies close to 69%. In conclusion SOFC is more efficiently integrated in a hybrid configuration with gas turbine and a steam turbine for trigeneration applications when pressurized. MCFC is more efficiently integrated at atmospheric and pressures below 6 atm.

Exergetic Performance Analysis of a Gas Turbine Cycle Integrated With Solid Oxide Fuel Cells

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Ibrahim Dincer ◽  
Marc A. Rosen ◽  
Calin Zamfirescu
Keyword(s):  
Power Generation ◽  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Gas Turbine ◽  
Integrated System ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Steam Generation ◽  
Energy And Exergy ◽  
Gas Turbine Cycle

Energy and exergy assessments are reported of integrated power generation using solid oxide fuel cells (SOFCs) with internal reforming and a gas turbine cycle. The gas turbine inlet temperature is fixed at 1573 K and the high-temperature turbine exhaust heats the natural gas and air inputs, and generates pressurized steam. The steam mixes at the SOFC stack inlet with natural gas to facilitate the reformation process. The integration of solid oxide fuel cells with gas turbines increases significantly the power generation efficiency relative to separate processes and reduces greatly the exergy loss due to combustion, which is the most irreversible process in the system. The other main exergy destruction is attributable to electrochemical fuel oxidation in the SOFC. The energy and exergy efficiencies of the integrated system reach 70–80%, which compares well to the efficiencies of approximately 55% typical of conventional combined-cycle power generation systems. Variations in the energy and exergy efficiencies of the integrated system with operating conditions are provided, showing, for example, that SOFC efficiency is enhanced if the fuel cell active area is augmented. The SOFC stack efficiency can be maximized by reducing the steam generation while increasing the stack size, although such measures imply a significant and nonproportional cost rise. Such measures must be implemented cautiously, as a reduction in steam generation decreases the steam/methane ratio at the anode inlet, which may increase the risk of catalyst coking. A detailed assessment of an illustrative example highlights the main results.

Effect of Fuel Cell Operation Pressure on the Optimization of a Hybrid System SOFC/Turbine for Cogeneration

2004 ◽  
Author(s):  
Georgia C. Karvountzi ◽  
Clifford M. Price ◽  
Paul F. Duby
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Hybrid System ◽  
Heat Balance ◽  
Gas Turbines ◽  
Solid Oxide ◽  
Oxide Fuel

A solid oxide fuel cell (SOFC) integrated in a hybrid system with a gas turbine can achieve lower heating value (LHV) power of efficiencies of about 70%. Given the high operating temperature of the SOFC, it produces high grade heat, and a hybrid system designed for cogeneration may achieve total LHV efficiencies of 78% of 80% without post combustion and 85%–88% with post combustion. The present paper illustrates the optimum integration of a tubular solid oxide fuel cell in a cogeneration cycle with a multiple pressure heat recovery steam generator (HRSG) and a back pressure steam turbine. We considered fuel cells of 7.5 MW, 9 MW, 15 MW, 15 MW, 18 MW, 22.5 MW and 27 MW by scaling up published data for a 1.2 MW tubular solid oxide fuel cell. The operating pressures were 3 and 9atm. We used GateCycle™ heat balance software by GE Enter Software, LLC, to design a 20–40 MW high efficiency cogeneration plant. We performed a calculation of the heat balance of the fuel cell stack in Microsoft® Excel and then we imported the results into GateCycle™. We developed curves showing LHV “electric” efficiency versus power for different ratios of “fuel cell-to-gas turbine size”. Pressurization has a positive impact on the fuel cell polarization curve leading to higher power output. The gain in electric power, however, is offset by the additional power requirement of the compressor at higher pressures. Our analysis shows that an optimum pressure of about 9 atmospheres results in an overall hybrid system power efficiency of about 70% and a LHV “cogeneration” efficiency of about 80%. In conclusion, high efficiencies are obtained by optimization of a hybrid system consisting of pressurized high temperature fuel cells with gas turbines and a steam turbine.

Thermodynamic model and analysis of hybrid power installations built around solid-oxide fuel cells and gas-turbine units

2008 ◽  
Vol 55 (9) ◽  
pp. 790-794 ◽  
Author(s):  
R. R. Grigor’yants ◽  
V. I. Zalkind ◽  
P. P. Ivanov ◽  
D. A. Lyalin ◽  
V. I. Miroshnichenko
Keyword(s):  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Gas Turbine ◽  
Thermodynamic Model ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Hybrid Power ◽  
Power Installations
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